A coup d'état is a sudden and illegal seizure of government power, typically executed by a small group, often including military leaders or political factions. The goal is to overthrow the existing government and replace it with a new authority, often without the consent of the general population. Coup d'états can lead to significant political instability and violence, as they disrupt the established order. Historical examples include the 1973 Chilean coup that overthrew President Salvador Allende and the 2014 Ukrainian revolution, which resulted in the ousting of President Viktor Yanukovych.